This invention is concerned with a biomedical clasp structure and especially, although not exclusively, with one capable of universal use, i.e., use with both kinds of external skin contacting electrode sensors (tab and snap types) now in use for substantially interference-free transfer of body or cardiovascular (CV) signals to electrocardiographic equipment for making ECG measurements, producing displays or for providing electrical stimulation to the body of a patient.
Disposable external electrode sensors for ECG readings are placed in contact with a patient at selected locations about the torso and limbs. These sensors are held adhesively to the skin surface and include a conductive gel or membrane that chemically reduces the resistance presented by the skin and thereby promotes the transmission of CV electrical impulses from the body of the patient via the electrodes to the associated detecting means. Two types of external disposable electrode sensors are in general use. The selection of either type is dependent on measuring conditions. One type used with the patient in a prone position for short-term measurements is a thin sheet form of electrode with an exposed planar tab for transferring sensed electrical signals. An alligator clip with jagged-edge gripping means has typically been used on an exposed planar contact tab. Another type of electrode generally used for longer-term measurements, for example, when the patient is exercising and/or being monitored for prolonged time periods, has a central metallic contact such as a male lug or nut.
As seen in FIG. 3 of U.S. Pat. No. 4,640,563 to LeBlanc, a prior art alligator clip includes jagged edge jaws at its working end and a handle for opening the jaws. As a part of the prior art connector structure, a lead wire is electrically connected by solder to one arm of the alligator clip. At the opposite longitudinal end of the lead wire, a female receptacle is provided for receiving a male member for electrical connection to the measuring equipment.
However, such an alligator clip has certain disadvantages and, in particular, cannot provide desired electrical contact and stability with a snap style contact stud. Because of the differing types of sensors and connectors, delays have occurred due to inferior and/or loose connections resulting in much frustration for the EKG operator since such connections can ruin the recording and prevent the machine from properly performing the test. Thus, it would require repeat tests and manual resecuring of prior art connections to the patient.
Because of the exposed lead wire, and other aspects of prior connectors, they could not be sterilized for repeated use in a sterile environment, had short-term life expectancy in non-sterile environments and, in general, did not provide optimum recovery of the low-energy-level patient signals available.
The present invention overcomes these problems and disadvantages by providing a single type of electrical clasp structure for obtaining accurate ECG measurements from the planar tab type electrode structures used for sensing patient signals, and allows for easy and rapid connection of a male connector leading to an electrical measuring and indicating device.
U.S. Pat. No. 4,061,408 describes a connector having an L-shaped lever arm. In the development of the present invention, it was found that such a lever is often awkward to use and is therefore not fully acceptable from a human engineering standpoint. In developing the present invention, it was noticed that the direction of lever rotation in U.S. Pat. No. 4,061,408 opposes the natural motion of the clasp itself as it is attached and later disconnected from the electrode. In addition, the patented clasp is only suited for the tab type of planar electrode. One important objective of the present invention is to overcome these deficiencies.
In contrast to the prior art, the present invention is well adapted for use with both the planar tab-type external electrode and the snap-type electrode in any type of patient monitoring or stimulation environment. It also provides a streamlined configuration. The structure can also be usefully employed, as well, in any so-called tab TENS (muscle stimulating electrode) environment and with other stimulation electrodes.
In addition, as specifically described in connection with FIGS. 15-31, it is a more specific object to provide a very secure, longitudinally distributed connection between upper and lower portions of the clasp housing; a secure, reliable but removable telescopic connection between the lead wire and the clasp; and an optional, non-metallic spring that is invisible to x-rays and consequently will not obscure anatomical structures that appear in x-ray films.